Daniel,

We found the open source geocoders not to be of high enough quality and intelligence to work effectively in common real-world free-text cases. Combined with data limits and a shared per-application ID, this wasn't worth pursuing.

However, I would not rule out developing something in future where the Omniscope user signs up and puts in their own application ID for this purpose.

Meanwhile, consider writing your own DataManager "Remote operation", a simple HTTP server that performs bulk geocoding in your own way using any of these services. This is an HTTP server that you develop, which receives typically CSV data via HTTP POST from DataManager, transforms it in any way (e.g. to add lat/lon data), and returns the resulting data to DataManager.

For this you need to know how to set up and write your own HTTP server. You can do this using Java Servlets, for example. Alternatively, you can hack this up with less know-how using Javascript on the server - here's a great example of how to write a simple HTTP REST service in node.js; ignore the database parts:
http://coenraets.org/blog/2012/10/creating-a-rest-api-using-node-js-express-and-mongodb/

If you have success with a particular provider and a particular kind of input data (text values), please post back here with the details of the provider and the data, so others can benefit, and so we can consider prioritising this.

Other ideas:

• MapBox - these guys have an API in private beta, which is expected to expand coverage, and has the unique ability to search through uploaded geo data of your own
  
• Downloading free government-provided data and using as lookup files in Omniscope - such as US zip codes and UK full post codes.